In a band saw, as the saw blade advances through the workpiece, pressures which are exerted on the blade by the operator, feeding mechanism or by the material itself, such as by knots or other irregularities in the material, cause the band saw blade to bend or flex from its normal position. It is this flexing which causes the blade to be deflected from its desired path as it moves through the workpiece. The deflection of the band saw blade as it goes through the workpiece causes an uneven cutting surface which is unpleasant to the eye and which must be further mechanically planed off to present a smooth appearance. The additional step of planing is uneconomical, in the sense that it involves an additional operation, and in addition causes a further waste in the wood product.
Some of the blade deflection could be eliminated with the use of a heavier gauge blade, such as is used in a circular saw. This, however, would mean that more material would be removed from the workpiece during the cutting operation. When this operation is repeated, it would be uneconomical in the sense that there would be a great amount of wood wasted. A band saw blade is particularly economical in that it is relatively thin, and thus presents a most economical means by which to cut wood.
The prior art devices which are used in conjunction with band saws have by and large proved to be extremely complicated and either rely on electronic circuitry for sensing blade deflection and making corrections therein, such as in the Wells patent (U.S. Pat. No. 3,680,417), or rely on very complicated mechanical means for again sensing the blade deflection and making the necessary corrections thereto (Kawabata, U.S. Pat. No. 3,259,155).
The devices such as shown in the above patents have a great disadvantage in that they are unnecessarily complicated and, in most instances, do not provide a satisfactory result. Generally, the blade deflection must be quite substantial before the electrical or mechanical sensing mechanism senses the deflection and initiates a steering action to correct the deviation. The present invention senses small deviations and makes the necessary corrections. The smaller the deflections, the easier it is to make the correction, and the more pleasant the appearance of the finished product.
Thus, it is the object of the present invention to supply a simple, yet accurate means for guiding a band saw blade.
It is further object of the present invention to provide a corrective twist to a band saw blade, to provide a straight and smooth cut surface. A further object of the present invention is to provide a device that is self-compensating, without electrical, hydraulic or mechanical circuitry to guide the band saw blade. A further object is to provide a device to prevent a band saw blade from drifting from the desired cutting path. Still other objects will readily present themselves to a skilled person with reference to the specification, the drawings and the claims of this patent.